(1) Field of the Invention
The present invention relates to a fixed length data processing apparatus, in particular, to a fixed length data processing apparatus suitable for use to execute operation, administration and maintenance (OAM) of ATM (Asynchronous Transfer Mode) communication using fixed length data of 53 bytes called an ATM cell.
(2) Description of Related Art ATM technique is.being introduced for the purpose of realization of B-ISDN (Broadband aspect of ISDN) communication network so as to comply with high speed (large capacity) communications, variable bit rate communications for image, communication systems having various connection configurations such as point-to-point, point-to-n points (n is 2 or more), n points-to-n points, and the like, required presently.
For instance, in SDH (Synchronous Digital Hierarchy) transmission network [called SONET (Synchronous Optical Network) in the North America], it is tried to map (store) signals for various communication services as ATM cells (fixed length data for asynchronous communication) onto a portion of payload of an SDH transmission frame [called STM (Synchronous Transfer Module), or STS (Synchronous Transport Signal) in SONET] and transmit the signal.
When an ATM cell is mapped onto the SDH transmission frame (hereinafter simply referred as a transmission frame, occasionally), a demand is to identify the ATM cell mapped onto the transmission frame in units of ATM cells and perform operation, administration and maintenance [a data (cell) processing such as a terminating processing on an OAM cell] at a level of ATM communication even in the SDH transmission network.
In a ring network 1xe2x80x2 configuring the SDH transmission network shown in FIG. 55, for example, it is necessary to interpose an ATM processing apparatus 4xe2x80x2 for performing the above cell processing between SDH transmitting apparatus 2xe2x80x2 and 3xe2x80x2.
Each of the SDH transmitting apparatus 2xe2x80x2 and 3xe2x80x2 has a function of mapping an ATM cell on or taking out (demapping) an ATM cell from a transmission frame. Since the ring network 1xe2x80x2 (SDH transmitting apparatus 2xe2x80x2 and 3xe2x80x2) accommodates a plurality of SDH transmitting apparatus 9xe2x80x2-1 through 9xe2x80x2-n (n is an integer not less than 2) which are transmission points in the lower hierarchy, as shown in FIG. 55, the ATM processing apparatus 4xe2x80x2 is required to perform the above cell processing on each transmission point. In concrete, it is necessary to separately perform the above cell processing on each transmission frame in a lower layer handled in each of the SDH transmission apparatus 9xe2x80x2-1 through 9xe2x80x2-n [distinguished as an STS channel #i (i=1 through n) in each of the SDH transmitting apparatus 2xe2x80x2 and 3xe2x80x2 (in a transmission frame in a higher layer)].
For this, each of the SDH transmitting apparatus 2xe2x80x2 and 3xe2x80x2 has mapping/demapping (MAP/DEMAP) units 2xe2x80x2-1 through 2xe2x80x2-n and 3xe2x80x2-1 through 3xe2x80x2-n according to the number of STS channels #i as shown in FIG. 56, for example. Each of the mapping/demapping units 2xe2x80x2-1 through 2xe2x80x2-n and 3xe2x80x2-1 through 3xe2x80x2-n includes a demapping unit 2xe2x80x2d or 3xe2x80x2d for taking out an ATM cell from a transmission frame in the upstream or in the downstream and outputting the ATM cell to the ATM cell processing unit 4xe2x80x2-i and a mapping unit 2xe2x80x2m or 3xe2x80x2m for storing (mapping) an ATM cell from the ATM cell processing unit 4xe2x80x2-i in a transmission frame in the upstream or in the downstream and outputting the ATM cell to another transmitting apparatus. The ATM processing apparatus 4xe2x80x2 has ATM cell processing units 4xe2x80x2-1 through 4xe2x80x2-n according to the number of the STS channels #i.
Each of the SDH transmitting apparatus 2xe2x80x2 and 3xe2x80x2 can thereby perform the above ATM cell mapping/demapping process for each STS channel #i by the mapping/demapping units 2xe2x80x2-1 through 2xe2x80x2-n and 3xe2x80x2-1 through 3xe2x80x2-n. The ATM cell processing unit 4xe2x80x2-i can perform the above cell processing for each STS channel
Namely, the ATM processing apparatus 4xe2x80x2performs the cell processing on ATM cells in transmission frames handled by each of the SDH transmitting apparatus 9xe2x80x2-1 through 9xe2x80x2-n separately for each STS channel #i by each exclusive ATM cell processing unit 4xe2x80x2-i serially.
For instance, an ATM cell from the SDH transmitting apparatus 9xe2x80x21, 9xe2x80x2-2, . . . or 9xe2x80x2-n in the lower hierarchy of the SDH transmitting apparatus 3xe2x80x2 is taken out from a transmission frame in the mapping/demapping unit 3xe2x80x2-1, 3xe2x80x2-2, . . . or 3xe2x80x2-n corresponding to, the STS channel #i, and sent to a corresponding ATM cell processing unit 4xe2x80x2-i according to an internal reference cell cycle of the ATM processing apparatus 4xe2x80x2.
Each of the ATM cell undergoes the cell processing in the ATM cell processing unit 4xe2x80x2-i corresponding to the STS channel #i, is mapped on a transmission frame in the corresponding mapping unit 2xe2x80x2-1, 2xe2x80x2-2, . . . or 2xe2x80x2-n, and transmitted to the SDH transmitting apparatus 9xe2x80x2-1, 9xe2x80x2-2, . . . or 9xe2x80x2-n accommodated in the lower hierarchy of the SDH transmitting apparatus 2xe2x80x2.
Each of the ATM cell processing units 4xe2x80x2-i identifies an ATM cell, and executes fault management [termination of an AIS (Alarm Indication Signal) or an RDI (Remote Defect Indication) cell] on an ALM (Alarm) cell of an OAM cell, mainly.
For instance, when the ATM processing apparatus 4xe2x80x2 receives an OAM (ALM) cell (VP/VC-AIS) indicating occurrence of a trouble within a certain VP/VC connection, the ATM processing apparatus 4xe2x80x2 notifies of a similar AIS the downstream, or when receiving an alarm (SONET alarm or the like) in a higher layer than AIS, the ATM processing apparatus 4xe2x80x2 generates a VP/VC-AIS/RDI cell and sends the cell to a desired destination.
For this, each of the ATM cell processing unit 4xe2x80x2-i has, as shown in FIG. 56, for example, a cell identifying unit 4xe2x80x2a, a cell generating unit 4xe2x80x2b, a cell inserting unit 4xe2x80x2c for downstream, a cell inserting unit 4xe2x80x2d for upstream, and a microcomputer I/F unit 4xe2x80x2e. 
The cell generating unit 4xe2x80x2b generates an ALM cell (VP-AIS, VC-AIS), and sends the cell to the downstream through the DnS cell inserting unit 4xe2x80x2c. On the other hand, an ALM cell (VP-RDI, VC-RDI) to be sent back is sent to the upstream through the UpS cell inserting unit 4xe2x80x2d. 
The microcomputer I/F unit 4xe2x80x2e has an interface used to set an operation channel, operation environments and the like from a system CPU or collect maintenance and management information (ALM information and the like).
The ALM cell or the like outputted from the ATM cell processing unit 4xe2x80x2-1, 4xe2x80x2-2, . . . , or 4xe2x80x2-n is again mapped on a transmission frame in the mapping/demapping unit 2xe2x80x2-1, 2xe2x80x2-2, . . . or 2xe2x80x2-n, and received by another apparatus which is a destination of the ALM cell.
When data (ATM cell) such as images having a larger volume of information is transmitted by applying VOD (Video on Demand) to the above ring network 1xe2x80x2, for example,a transmission capacity of the ring network 1xe2x80x2 is increased. When a transmission rate of the ring network 1xe2x80x2 is increased as above, a rate of occurrence of ATM cell loss, misinsertion and the like in the network (ATM communication) is increased with an increase of quantity of data (ATM cell) flow.
In particular, when a network structure (connection configuration) for a large capacity transmission of one point-to-n points or n points-to-n points, a variable bit rate communication and the like becomes complex, an increase of rate of occurrence of ATM cell loss, misinsertion and the like is noticeable.
Therefore, it is necessary to monitor an operation state of the network to detect the above cell loss or misinsertion and monitor a flow state in addition to the OAM. However, the ATM processing apparatus 4xe2x80x2 shown in FIG. 56 executes only a fault management on ATM cells, not executing detection of cell loss and the like.
In the light of the above problems, an object of the present invention is to provide a fixed length data processing apparatus which can detect loss or misinsertion of fixed length data as an ATM cell, and monitor a flow state of the fixed length data in a transmission system having a high transmission rate.
The present invention therefore provide s a fixed length data processing apparatus processing fixed length data used in an asynchronous communication comprising a data processing unit for receiving at least the fixed length data and performing a desired data processing on the fixed length data, and an operation state monitoring process unit for performing a monitoring process to monitor an operation state of the asynchronous communication on the basis of the fixed length data received by the data processing unit.
According to this invention, the fixed length data processing apparatus can readily detect loss, misinsertion and the like of the fixed length data, and execute maintenance and management such as monitoring on a flow state and the like in a high speed communication.